Carbonates
The bitumen residing in the Devonian carbonates of Northern Alberta displays molecular evidence indicating they represent some of the most biodegraded and altered petroleum accumulations in the world. The bitumen API gravities range from 5 to 9, whereas viscosities may reach several million centipoises at reservoir temperatures, often showing complex viscosity variations within a reservoir. Due to these inherent physical properties, the recovery of bitumen from carbonates proves to be challenging in the field and in the laboratory.
At Gushor, we have successfully developed methods for measurement and determination of the physical and chemical properties of heavy oil and bitumen in oil sands. We have now tailored these methods towards bitumen recovery from carbonate reservoir samples, thereby allowing direct measurement of viscosity and API gravity.
The approaches:
1) PlungerTM: Recovery of bitumen from carbonates is practiced in a similar manner to processing oil sands.
2) GviscTM: When the bitumen is too viscous to flow from the plunger device or oil saturation is low, the ability of a specially tailored solvent cocktail to mobilize bituemen from carbonate samples readily allows direct viscosity measurements using the Gvisc method.
3) PROXVISCTM: Based on coupling quantitative bitumen composition to viscosity by neural networks or multivariate statistics, viscosity can be assessed geochemically. In addition, the bitumen composition fingerprint may provide an indication of oil quality through recognizing the presence or absence of specific biodegradation sensitive compounds. This method can be applied to old core and give very high spatial resolution data.
